Traction motor temperature control of locomotive power

ABSTRACT

A system for controlling the power output of the generator of a locomotive as a function of the temperature of the traction motors connected to the generator. The system utilizes an electrical heater element connected in series with at least one traction motor and the heater generates an amount of heat which is a function of the amount of current being supplied to the traction motor. The heater element forms part of a simulator such that the temperature developed by it simulates the operating temperature of the traction motor for a given traction motor current. A temperature sensitive resistance element senses the temperature of the simulator and is connected with a control circuit so as to vary the excitation and output power of the generator as a function of the temperature sensed by the resistance element. The simulator and traction motors are arranged such that they both are at substantially the same ambient temperature.

United States Patent [72] Inventors MaxEphraim,Jr.

Evergreen Park; Earl D. Smith, Naperville, both of ill. [21] Appl. No.26,861 [22] Filed Apr. 9, 1970 [45] Patented Dec. 21, 1971 [7 3]Assignee General Motors Corporation Detroit, Mich.

[54] TRACTION MOTOR TEMPERATURE CONTROL [56] References Cited UNITEDSTATES PATENTS 3,225,280 12/1965 Happe et a1 318/473 3,004,201 10/1961Fath 318/158 3,346,772 10/1967 Mierendorf 3,527,991. 9/1970 SackinABSTRACT: A system for controlling the power output of the generator ofa locomotive as a function of the temperature of the traction motorsconnected to the generator. The system utilizes an electrical heaterelement connected in series with at least one traction motor and theheater generates an amount of heat which is a function of the amount ofcurrent being supplied to the traction motor. The heater element formspart of a simulator such that the temperature developed by it simulatesthe operating temperature of the traction motor for a given tractionmotor current. A temperature sensitive resistance element senses thetemperature of the simulator and is connected with a control circuit soas to vary the excitation and output power of the generator as afunction of the temperature sensed by the resistance element. Thesimulator and traction motors are arranged such that they both are atsubstantially the same ambient temperature.

TRACTION MOTOR TEMPERATURE CONTROL OF LOCOMOTIVE POWER This inventionrelates to a power control system for controlling the power output of alocomotive traction motor generator which supplies traction motors andto a system wherein the output voltage of the generator is controlled bya device which simulates traction motor temperature.

When operating a locomotive that utilizes an engine driven generatorthat supplies current to a plurality of traction motors the power outputof the generator is controlled such that the traction motors will notbecome overheated particularly during low speed operation of thetraction motors for example when the locomotive is moving up a ratherlong grade. The stems that have been used for controlling the outputpower of the generator have been controlled as a function of the speedof a traction motor. This means that whether the locomotive is moving upa short grade or relatively long grade the output power to the tractionmotor will be limited with prior art systems when the speed of thetraction motor drops to a certain value so as to ensure that thetraction motors will not be overheated.

It will be appreciated that where power output is controlled as afunction of traction motor speed there will be conditions of operationwhere the motor could actually be operated at a higher current levelthan that dictated by a speed responsive system with the result that thelocomotive system is not at all times operating at its highest possiblepower level.

In contrast to systems that control power output of the generator as afunction of traction motor speed it is an object of this invention toprovide a system for controlling the power output of the generator as afunction of traction motor temperature whereby limiting does not takeplace until the temperature of the traction motor reaches a level wherecontinued operation at this temperature might harm the traction motor.In carrying this object forward an electrical heating element isconnected in series with a traction motor and is arranged such that thetemperature the heater element attains is a function of traction motorcurrent and also simulates traction motor temperature for a giventraction motor current.

It accordingly is another object of this invention to provide alocomotive traction motor power supply system wherein the excitation ofthe main power generator is controlled as a function of the heatgenerated by a heater element that is connected in series with atraction motor but which is located outside of the traction motor. Withthis arrangement the difficulties of actually physically placing adevice in the traction motor to sense a temperature of a part of thetraction motors during railroad use.

Still another object of this invention is to provide a power controlsystem for a locomotive wherein a heater element is connected in serieswith the traction motor and wherein the heater element forms part of asimulator that develops a temperature which simulates the operatingtemperature of the traction motor as a function of current supplied tothe traction motor and further wherein a temperature sensitiveresistance senses the temperature of the simulator and is coupled to acontrol circuit that controls the excitation of the main powergenerator. IN THE DRAWINGS FIG. 1 is a schematic circuit diagram of alocomotive power control system made in accordance with this invention;

FIG. 2 is a plan view of a motor temperature simulator which forms acomponent part of the power control system of this invention;

FIG. 3 is a plan view of a temperature detector which is attached to themotor temperature detector which is attached to the motor temperaturesimulator shown in FIG. 2;

FIG. 4 is a top view of the motor temperature simulator shown in FIG. 3with the resistance temperature detector of FIG. 3 attached thereto; and

FIG. 5 illustrates a system for supplying air to the traction motors ofthe power supply system of this invention and to the motor temperaturesimulator.

Referring now to the drawings and more particularly to FIG. I, thereference numeral designates a main power supply generator for thetraction motors of a locomotive. The generator 10 is an alternatingcurrent generator having a three phase Y-connected stator winding 12 anda field winding 14 which may be mounted on the rotor of the generator.The rotor is driven by an engine which is not illustrated. The outputvoltage of the stator winding 12 is applied to a three phase fullwavebridge rectifier designated by reference numeral 16 and having directcurrent output terminals connected with traction motor power supplyconductors l8 and 20. The power supply system can take variousconfigurations and may include for example a number of Y-connectedwindings connected with a number of bridge rectifiers as is disclosed inthe US. Pat. to Thiessen No. 3,340,448, issued on Sept. 5, 1967. Thedirect current power supply conductors l8 and 20 supply conventionaldirect current series traction motors 22 and 24 which are shownconnected in parallel across the power supply conductors l8 and 20. Thearmatures of the traction motors are, of course, coupled to the wheelsof the locomotive in a conventional manner which is not illustrated.

The traction motor 24 is connected in series with an electrical heatingelement designated by reference numeral 26. This heating element isdescribed in detail hereinafter it being pointed out, however, that thisheating element generates heat as afunction of the amount of currentbeing supplied to the traction motor 24. As will be describedhereinafter the heating element 26 together with its mounting provide atemperature simulator which simulates the actual operating temperaturewithin the traction motor 24 and particularly simulates the temperatureof the series field of this motor.

The temperature of the heating element 26 is sensed and is utilized tocontrol the excitation of the field winding 14 of the main powergenerator 10. To this end a temperature sensitive resistance designatedby reference numeral 28 is positioned to sense the temperature of thesimulator including heater element 26 and thereby vary the resistanceacross its terminals 30 and 32 as a function of the temperature sensed.This resistance element has a positive temperature coefficient ofresistance and its physical construction is fully described hereinafter.

In order to control the excitation of the field winding 14 of the mainpower generator 10 as a function of the temperature of the heaterelement 26 the temperature sensitive resistance 28 is coupled to acontrol system which will now be described for varying field excitation.It is seen that the temperature sensitive resistance 28 forms part of aWheatstone bridge designated by reference numeral 34 which also includesresistors 36, 38 and 40. The input terminals 42 and 44 of the bridge areconnected with a source of direct current which in this case takes theform of a single-phase bridge rectifier 46 connected with the secondarywinding 48 of a transformer 50. The primary winding 52 of thetransformer is connected across power supply conductors 54 and 56 fedfrom a single phase source of alternating current as describedhereinafter. The primary winding 52 is connected in series with aresistor 58 and a pair of Zener diodes are connected across the primarywinding 52 as illustrated in FIG. 1 to provide some voltage regulation.

The output terminals 60 and 62 of the Wheatstone bridge are connectedwith the base-emitter circuits of transistors 64 and 66 which areconnected in a Darlington configuration. The output terminal 62'of theWheatstone bridge 34 is connected with a conductor 72. The conductor 72is connected with the negative side of a source of direct current 68through a resistor 65. The positive side of the source of direct currentis connected with a junction 67 which in turn is connected with aconductor 69. The conductor 69 is connected to one side of seriesconnected direct current control or sensor windings 70 of a magneticamplifier to be described hereinafter. The opposite sides of the controlwindings 70 are connected with a conductor 71 which in turn is connectedto the collector of an NPN-transistor designated by reference numeral73. The emitter of transistor 73 is connected with a diode 75 and thecathode of this diode is connected to junction 77 and to conductor 76which is connected to the collectors of transistors 64 and 66. Ittherefore is seen that the collector-emitter circuit of transistor 66and resistor 65 are connected in series across conductors 76 and 72 andtherefore in parallel with a resistor 79. The junction 77 is locatedbetween resistors 79 and 81 and these resistors are connected in seriesacross a direct voltage source designated by reference numeral 83. Thedirect voltage source 83 preferably takes the form of a bridge rectifier(not illustrated) which receives alternating current from currenttransformers, not illustrated, including windings that sense the currentin the conductors connecting the output winding 12 of the generator withthe bridge rectifier 16. Such current transformers are well known tothose skilled in the art and it therefore will be understood that thedirect voltage source 83 develops a direct voltage the magnitude ofwhich is a function of the current flowing in the conductors supplyingthe bridge rectifier 16. This provides a cur-' rent feedback voltagewhich is known to those skilled in the art and this feedback voltagedevelops a potential at junction 77 to thereby control the potential ofthe emitter of transistor 73.

The base of transistor 73 is connected with a rheostat designated byreference numeral 85 and connected across the direct current source 68.The adjustable slider or arm 85A of the rheostat 85 is controlled by aload regulator which adjusts the arm 85A in accordance with the settingof an engine governor (not illustrated) as is known to those skilled inthe art to adjust the power output of a locomotive system. As is knownto those skilled in the art the adjustment of the load regulatorrheostat 85 by an engine governor sets the output power level for thegenerator 10.

It will be appreciated that the amount of current supplied to thecontrol windings 70 of the magnetic amplifier will be function of theconductance of transistor 73 in its collector-emitter current. Theconductive or nonconductive mode of transistor 73 depends upon therelative base to emitter voltage with the base voltage being set by theload regulator. The emitter voltage of transistor 73 is controlled as afunction of the feedback voltage 83 and also as a function of theconduction of transistors 64 and 66. Thus, when transistors 64 and 66are conducting, as when the temperature sensed by resistor 28 is below apredetermined value, the resistor 65 is connected in parallel withresistor 79. The values of the resistors are so proportioned that whentransistors 64 and 66 conduct the potential at junction 77 is reducedwith the result that more current can be supplied to the magneticamplifier coils 70 through transistor 73 and with the further resultthat the power output of the generator can be increased. This means thatwhen the temperature developed by the temperature simulator, includingthe heater 26, is below a limiting value the excitation of the generator10 can be increased to a certain value.

When the temperature sensed by resistor 28 reaches the limiting valuethe transistors 64 and 66 are biased nonconductive with the result thatresistor 79 controls the excitation level of the generator and limits itto some value determined by the current feedback and setting of loadregulator rheostat 85. Over a predetermined range of temperatures,however, and up to the limiting temperature the temperature sensitiveresistor is continuously controlling the excitation of the generator 10and permitting it to be excited at a maximum current for a giventemperature. The transistors 64 and 66 operate in a modulating modeduring variation of temperature over a predetermined temperature range.It should be further pointed out that resistors 36, 38 and 40 of theWheatstone bridge have equal resistance values and the resistance of oneof these resistors is equal to the resistance of circuit element 28 whenit has a predetermined temperature.

The amount of direct current applied to the DC control winding 70controls the excitation of the field winding 14 of the main powergenerator 10. To this end the system includes a three phase auxiliarygenerator designated by reference numeral 80 which feeds a three phasefull-wave bridge designated by reference numeral 82 and comprised ofthree diodes 84 and three controlled rectifiers 36, 88 and 90. The powersupply conductors 92, 94 and 96 supply the bridge rectifier throughconductors 98, 100 and 102 and also supply three phase power to theprimary windings 104, 106 and 108 of a transformer 110. Conductors 94and 96 are connected to conductors 54 and 56 and therefore apply singlephase power to these conductors. The secondary windings of thetransformer 110 are designated by reference numerals 112, 114 and 116.Each secondary winding is connected in series with a diode 118, asaturable reactor coil and a resistor 122. The reactor coils 120 formpart of a magnetic amplifier the saturation of which is controlled bydirect current supplied to the direct current coils 70 of the magneticamplifier. These saturable or magnetic amplifiers preferably have DCbias windings which, for purposes of this invention, have not beenillustrated.

It is seen that the respective gate electrodes of controlled rectifiers86, 88 and 90 are coupled to one side of the resistors 122 whereas thecathodes of these controlled rectifiers are all connected to conductor124 and to an opposite side of the resistors 122 via a conductor 126connected to conductor 124.

The conductors 124 and 128 of the bridge 82 supply direct current to thefield winding 14 of the main power generator 10 through conductors 130and 132. The firing angle of the controlled rectifiers 86, 88 and 90 iscontrolled by the magnetic amplifier whereby the direct current suppliedto field winding 14 is controlled as a function of bias current incontrol windings 70 of the magnetic amplifier and the magnitude of thiscurrent is a function of the resistance of the temperature sensitiveresistance element 28. In this regard it is pointed out that the reactorcoils 120 of the magnetic amplifier will saturate at some predeterminedvalue of direct current applied to control coils 70. As the currentthrough the control or sensor coils 70 is increased the reactorssaturate earlier in the cycle of applied alternating current. When thereactor coils 120 saturate their impedance drops with the result thatthe voltage across resistors 122 increases to a value which issufficient to gate the controlled rectifiers 86, 88 and 90 conductive.It therefore will be appreciated that as the resistance of temperaturesensitive resistor 28 decreases from a predetermined value the magneticamplifier is saturated earlier in the cycle of applied voltage with theultimate result that more current can be supplied to field winding 14.When the temperature sensed by resistor 28 reaches a predetermined valueto bias transistors 64 and 66 nonconductive the conduction of transistor73 will be controlled such that a minimum amount of conductance fortransistor 73 is due to temperature control. Between the value ofresistance 28, which causes nonconduction of transistors 64 and 66 and alower resistance value corresponding to a lower simulated traction motortemperature, the conduction of transistors 64 and 66 is modulated totherefore apply a bias to transistor 73 to smoothly vary the excitationof field winding 14 over a predetermined range of temperatures. It ispointed out that the phase relationship of the voltages on conductors92, 94 and 96, the polarities of the transformers, and the connection ofthe phases of generator 80 with the bridge 82 are all arranged so thatthe signal voltage applied to the gates of the controlled rectifiers isin phase with the voltages applied to the bridge by conductors 98, 100and 102. This means that the firing angle of the controlled rectifiersis controlled by the firing angle of the saturable reactor coils 120 toprovide accurate control of current supplied to field winding 14. Itwill, of course, be appreciated that the controlled rectifiers 86, 88and 90 are commutated by the alternating output voltage of generator 80.

Although a specific control circuit, including transistors 64, 66 and73, has been described together with the magnetic amplifier and thebridge 82 for regulating the field current of field winding 14 it willbe appreciated that other control systems could be utilized as long asthe field current is controlled over a predetermined temperature rangeof the simulator by the temperature sensitive resistance 28. It shouldbe further appreciated that the control transistor 73 is controlled by anumber of parameters in the system other than the simulated temperatureof a traction motor.

Referring now to FIG. 2, the physical construction of the motortemperature simulator, which includes the resistance element 26 will nowbe described. As seen in FIG. 2 the motor temperature simulator which isgenerally designated by reference numeral 140 comprises two blocks 142and 144 which are formed of copper. Each block has a ledge portion 142Aand 144A to which is attached at the underside of the ledge portions theresistance heater element 26. The resistance heater element 26 is a flatelongated strip of metallic material preferably of a nickel-chromiumalloy commonly known as a resistance alloy. As an example the materialutilized for part 26 should have a relatively high electricalresistivity for example a resistivity of 543 ohms per square mil ft. ata temperature of C. A material which is suitable for this purpose isAllegheny Ludlum Ohmaloy which has the abovementioned resistivity and arelatively low temperature coefficient of resistance. The strip, ofcourse, operates as an electrical heating element and the amount of heatdeveloped by the strip will be a function of the resistance of the stripand the square of the current passed therethrough. The heater strip 26is attached to the underside of ledges 142A and 144A by silver solderingthis part to the copper blocks.

The mass of the copper blocks and the amount of heat developed by theheater strip 26 are so calculated with respect to temperaturesencountered in a traction motor for a given traction motor current thatthe temperature developed by simulator 140 closely simulates that whichwould be actually encountered within the traction motor and particularlythe series field of the traction motor. In this regard the mass ofcopper blocks 142 and 144 to some extent slows down the general heatingeffect but the copper mass and the amount of heat generated by theheater strip 26 all provide temperature conditions which very nearlysimulate the exact temperature conditions found in the traction motor.As will be further explained hereinafter the motor temperature simulatoris located outside of the housing of the traction motor and preferablyin an electrical equipment cabinet on the locomotive. In addition, thesame air which is used to cool the traction motors is also applied tothe motor temperature simulator 140 so that the traction motor and motortemperature simulator 140 are both located within the same environmenttemperature. This is morefully described hereinafter in connection withFIG. 5 which illustrates the relative positions of the traction motorsand motor temperature simulator 140 on a locomotive and how air isdirected to the traction motors and the motor temperature simulator.

The temperature which is attained by the motor temperature simulator 140is sensed by a temperature sensitive resistance having a positivetemperature coefficient of resistance which is identified by referencenumeral 28 in FIG. 1. The actual physical construction of thetemperature sensing device is shown in FIG. 3. This temperature detectoris generally designated by reference numeral 150 in FIG. 3 and includesan aluminum housing designated by reference numeral 152. The temperaturesensitive resistance element 28 is secured but insulated from he bottominner wall of the housing 152 which carries a plastic housing designatedby reference numeral 154. The terminals 30 and 32 of the temperaturedetector 150. which are connected to opposite sides of resistor 28,project from the top side of the plastic housing 154 and as shown inFIG. I become connected with the Wheatstone bridge 34.

The temperature detector 150 is secured to the copper block 142 oftemperature simulator 140 in a manner illustrated in FIG. 4. Thetemperature detector is secured to the copper block 142 by screws 151that are threaded into the copper block 140 and which pass throughopenings formed in the brackets 156 and 158 of the temperature detectordirectly contacts the top side of the ledge 142A of copper block 142. Itwill therefore be appreciated that heat generated by the flat heater 26will be conducted to the temperature sens itive resistance 28 by copperblock and through the lower wall of aluminum housing 152 and this wallis again proportioned so that the temperature sensed by the resistor 128closely simulates the actual temperature conditions in a traction motorfor a given level of traction motor current. The mounting of thetemperature detector on ledge 142A of reduced thickness has been foundto give particularly accurate temperature simulation and detection.

The blocks 142 and 144 are bolted to bus bars not illustrated whichconnect the simulator in series with a traction motor. These bolts passthrough the holes in the blocks 142 and 144.

As has been pointed out previously the temperature detector is notdisposed within the traction motor but rather in an electricalcompartment of the locomotive. FIG. 5 illustrates the remote location ofthe motor simulator 140 and temperature detector from the tractionmotors 22 and 24 and also illustrates schematically the means forplacing the traction motors and the temperature simulator and detectorin the same temperature environment.

In FIG. 5 the reference numeral designates a traction motor blower whichsupplies air to a duct 162 connected with ducts 164 and 166. The ducts166 and 164 direct this air into the housings of the traction motors 22and 24 in a conventional manner in order to cool the traction motors.The inlet side of blower 160 is connected with an inlet air duct 168which receives air pulled into the locomotive from the exterior of thelocomotive. This air is therefore at the same temperature as the outsideair.

The motor temperature simulator 40 and the temperature detector 150 arelocated in an electrical cabinet on a locomotive which is notillustrated. The duct 162 is connected to a duct 170 which feeds acompartment 172 having orifices for directing air onto the motortemperature simulator 140 in a manner illustrated in FIG. 5. Because ofthis arrangement it will be appreciated that the traction motors 22 ans24 and the motor temperature simulator 140 are both subjected to air ofthe same temperature since the outlet side of the blower 160 feeds airto both the traction motors and the motor temperature simulator 140.This means that the traction motors and the motor temperature simulatorare subjected to the same ambient temperature and the temperature sensedby the temperature sensitive resistance 28 is therefore a trueindication of actual temperature conditions in the traction motors for agiven traction motor current since the motor temperature simulator 140provides substantially this same temperature.

The overall operation of the power control system of this invention willnow be described. As the generator 10 supplies current to the tractionmotors 22 and 24 the excitation of its field winding 14 is controlled totherefore control the output power developed by the generator. Thisexcitation can be varied by a number of factors including the loadregulator rheostat 85. It will be appreciated that when a predeterminedmaximum temperature is attained, as sensed by temperature sensor 28 theWheatstone bridge will be balanced with the result that transistors 64and 66 are substantially nonconductive with the further result thatexcitation is limited due to the bias applied to transistor 73. Themagnetic amplifier is arranged such that the conduction period of thecontrolled rectifiers 86, 88 and 90 increases with increasing currentthrough the bias windings 70 and decreases as the current is reduced inthese bias windings. This means that with the transistors 64 and 66nonconductive the output voltage of the bridge 82 and consequently thefield excitation of field winding 14 is limited when the limitingtemperature condition is encountered.

As the temperature of the motor temperature simulator 140 decreases, forexample due to less current being supplied to traction motor 24 or torelatively cold outside temperature conditions, the resistance oftemperature sensitive resistor 28 decreases with the result that thetransistors 64 and 66 are biased on to some extent. This means that morebias current can be supplied to control coils 70 with the further resultthat the output voltage of bridge 82 can be increased to increase theexcitation of field 14 and therefore the output voltage and power ofgenerator 10. The transistors 64 and 66 operate in a modulating mode sothat the bias to transistor 73 is smoothly varied over a predeterminedtemperature range sensed by resistor 28 to therefore provide one factorin determining the field excitation and output power of the generator10. In this regard it will of course be appreciated that adjustment ofthe load regulator rheostat 85 sets a power level for the generator 10and transistor 73 is conductive as long as its base voltage exceeds itsemitter voltage to therefore cause current to be supplied to controlwinding 70. The conduction of transistor 73 is therefore determined bythe relative voltages at arm 85A and the voltage of junction 77. Thevoltage at junction 77 is determined by current feedback and also by thetemperature attained by the temperature simulator 140. This means thatwhen the temperature of the temperature simulator is below a limitingvalue the excitation of the field winding 14 can be increased to ahigher value than a condition where the temperature simulator reaches alimiting value. This is determined by the potential at junction 77 whichis varied as the conduction of transistors 64 and 66 vary to therebyprovide a temperature control parameter to the excitation of fieldwinding 14. It should be pointed out that the emitter of transistor 73can also be supplied with a bias voltage which is a function of theoutput voltage of generator 10. This can be accomplished by sensing theoutput voltage of the output winding 12 with transformers which feed abridge rectifier which provides a direct voltage that is a function ofthe output voltage of the output winding 12. In any event, for purposesof this invention, the field excitation is controlled and limited as afunction of the temperature sensed by the resistor 28 and other controlschemes could be utilized to perform this function.

it will, of course, be appreciated that the generator 10 and thegenerator 80 are both driven by a suitable prime mover on a locomotivesuch as a diesel engine which has not been illustrated.

We claim:

1. A power control system for an electric motor comprising, a generatorhaving an output winding and a field winding, an electric motor adaptedto be drivably connected with a load, means connecting said motor withsaid output winding of said generator, a motor temperature simulatorcomprising an electrical heater and a block of heat conductive materiallocated in heat exchange relationship with said heater, means connectingsaid electrical heater in series with said motor, said simulator beingdisposed outside of said motor, said simulator developing a temperaturewhich is a function of motor current whereby said temperature is relatedto the internal temperature of said motor, temperature detection meanscomprising a temperature sensitive resistor located in heat exchangerelationship with said block of heat conductive material for sensing thetemperature of said simulator, control means coupled to said temperaturesensitive resistor and to said field winding of said generator forcontrolling the excitation of said field winding of said generator forcontrolling the excitation of said field winding as a function of thetemperature developed by said simulator, and means subjecting saidsimulator and the interior of said motor to substantially the sametemperature environment.

2. A power control system for a vehicle comprising, a main powergenerator having an output winding and a field winding, a direct currentseries traction motor adapted to be coupled to a wheel of said vehicle,means electrically connecting said traction motor with said outputwinding of said generator, a temperature simulator comprising anelectrical heating element located in heat exchange relationship with ablock of heat conductive material, means connecting said heating elementin series with said traction whereby said heating element generates heatas a function of the magnitude of traction motor current to therebycause said temperature simulator to develop a temperature which is afunction of the internal temperature of said traction motor, temperaturedetection means comprising a temperature sensitive resistor located inheat exchange relationship with said block of heat conductive material,control means connected with said temperature sensitive resistor andsaid field winding of said generator for controlling the excitation ofsaid field winding of said generator as a function of the temperature ofsaid simulator, said simulator and temperature detector being disposedoutside of said traction motor, and means subjecting said simulator andtemperature detector to a temperature environment that is substantiallythe same as that of the interior of said traction motor.

3. A power control system for a vehicle comprising, a main powergenerator having an output winding and a field winding, a series directcurrent traction motor adapted to be coupled to a wheel of said vehiclefor driving said wheel, means electrically connecting said tractionmotor and comprising an electrical heating element located in heatexchange relationship with a block of heat conductive material, meansconnecting said heating element in series with said motor, said heatingelement and block of conductive material proportioned such that saidsimulator develops a temperature which substantially simulates theinternal temperature of said traction motor for a given traction motorcurrent, a temperature detector comprising a temperature sensitiveresistor disposed adjacent said simulator for sensing the temperature ofsaid simulator, control means coupled to said temperature sensitiveresistor and to said field winding of said generator for varying theexcitation of said field winding as a function of the temperature sensedby said temperature detector, and means for supplying cooling air to theinterior of said traction motor and to said temperature simulator tothereby subject the interior of said traction motor and said temperaturesimulator to substantially the same temperature environment.

4. A power control system for a vehicle comprising, a generator havingan output winding and a field winding, a traction motor adapted to beconnected with a wheel of said vehicle for propelling said vehicle,means connecting said traction motor with said output winding of saidgenerator, a traction motor temperature simulator comprising anelectrical heater and ablock of heat conductive material located in heatexchange relationship with said heater, means connecting said electricalheater in series with said traction motor, said simulator being disposedoutside of said traction motor, said simulator developing a temperaturewhich is a function of motor current whereby said temperature is relatedto the internal temperature of said traction motor, a temperaturesensitive resistor located in heat exchange relationship with said blockof heat conductive material for sensing the temperature of saidsimulator, control means coupled to said temperature sensitive resistorand to said field winding of said generator for controlling theexcitation of said field winding as a function of the temperaturedeveloped by said simulator, and means subjecting said simulator and theinterior of said traction motor to substantially the same temperatureenvironment.

gg gg UNITED STATES PATENT @FHCE CERTIFICATE @i QURREC'MQN Patent N0.Dat d December 21 Inventork's) Max Ephraim, Jr, et Ell.

It is certified that error appears in the above-identified patent I andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 14, "stems" should be systems ----2 line 47, aftertreotion insert motor is eliminated as is the likelihood of damage tothe sensing device from debris and other elements enoountered bytraction lines 65 and 66, delete "detector which is attached to themotor temperature Column 2, line 35, after "and" insert to Column 3,line 33, after "he" insert a ---e Column 4, line 1, "36" should be 86line 62,, after "of" insert the Column 5, line 44, after "ture" insertwise and therefore respond to the same ambient temperature line 58, heshould be the ----3 line 70, after 'deteetor" insert mu 0 The brackets156 and l58 are secured to housing 152. The lower well of aluminumhousing 152 of the temperature detector Column 6, line 36, "ans" shouldbe and Column 7, lines 56 and 57, delete "of said generator foroontrolling the excitation of said field winding Column 8, line 6, aftertraction insert motor line 25, after "motor" insert with said outputwinding of said generator, a traction motor temperature simulatorlocated outside of said traction motor Signed and sealed this 27th dayof June 1972,

(SEAL) .J

Attest:

EDWARD M.FLETCHER,JR, ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents mg nnntn STATES PATENT orntr QERTHMCATE @l QQRREQTWN PatentNo 3,629,676 D t d December 21,

Inven 0r(s) Max Ephraim; Jr, et ale It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line l4 "stems" should be systems line 47, after "tractioninsert motor is eliminated as is the likelihood of damage to the sensingdevice from debris and other elements encountered by traction lines 65and 66,, delete "detector which is attached to the motor temperatureColumn 2, line 35, after "and" insert to ----o Column 3, line 33, after"he" insert a --o Column 4, line 1,, 36" should be 86 line 6? after "of"insert the -----o Column 5, line 44-, after "ture" insert -wise andtherefore respond to the same ambient temperature line 58 "he" should hethe line 76 after "detector" insert 6 The brackets 15% and l58 areseeured to housing 152., The lower well of aluminum housing 152 of thetemperature detector -o Column 6, line 36 "ans" should be and a Column 7lines 56 and 57, delete "of said generator for controlling theexcitation of said field winding e Column 8, line 6 after "traction"insert motor line 25 after "motor" insert with said output winding ofsaid generator, a traction motor temperature simulator located outsideof said traction motor e Signed and sealed this 27th day of June 19720-(SEAL) J Attest:

EDWARD MQFLETCHER JRQ ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. A power control system for an electric motor comprising, a generatorhaving an output winding and a field winding, an electric motor adaptedto be drivably connected with a load, means connecting said motor withsaid output winding of said generator, a motor temperature simulatorcomprising an electrical heater and a block of heat conductive materiallocated in heat exchange relationship with said heater, means connectingsaid electrical heater in series with said motor, said simulator beingdisposed outside of said motor, said simulator developing a temperaturewhich is a function of motor current whereby said temperature is relatedto the internal temperature of said motor, temperature detection meanscomprising a temperature sensitive resistor located in heat exchangerelationship with said block of heat conductive material for sensing thetemperature of said simulator, control means coupled to said temperaturesensitive resistor and to said field winding of said generator forcontrolling the excitation of said field winding of said generator forcontrolling the excitation of said field winding as a function of thetemperature developed by said simulator, and means subjecting saidsimulator and the interior of said motor to substantially the sametemperature environment.
 2. A power control system for a vehiclecomprising, a main power generator having an output winding and a fieldwinding, a direct current series traction motor adapted to be coupled toa wheel of said vehicle, means electrically connecting said tractionmotor with said output winding of said generator, a temperaturesimulator comprising an electrical heating element located in heatexchange relationship with a block of heat conductive material, meansconnecting said heating element in series with said traction wherebysaid heating element generates heat as a function of the magnitude oftraction motor current to thereby cause said temperature simulator todevelop a temperature which is a function of the internal temperature ofsaid traction motor, temperature detection means comprising atemperature sensitive resistor located in heat exchange relationshipwith said block of heat conductive material, control means connectedwith said temperature sensitive resistor and said field winding of saidgenerator for controlling the excitation of said field winding of saidgenerator as a function of the temperature of said simulator, saidsimulator and temperature detector being disposed outside of saidtraction motor, and means subjecting said simulator and temperaturedetector to a temperature environment that is substantially the same asthat of the interior of said traction motor.
 3. A power control systemfor a vehicle comprising, a main power generator having an outputwinding and a field winding, a series direct current traction motoradapted to be coupled to a wheel of said vehicle for driving said wheel,means electrically connecting said traction motor and comprising anelectrical heating element located in heat exchange relationship with ablock of heat conductive material, means connecting said heating elementin series with said motor, said heating element and block of conductivematerial proportioned such that said simulator develops a temperaturewhich substantially simulates the internal temperature of said tractionmotor for a given traction motor current, a temperature detectorcomprising a temperature sensitive resistor disposed adjacent saidsimulator for sensing the temperature of said simulator, control meanscoupled to said temperature sensitive resistor and to said field windingof said generator for varying the excitation of said field winding as afunction of the temperature sensed by said temperature detector, andmeans for supplying cooling air to the interior of said traction motorand to said temperature simulator to thereby subject the interior ofsaid traction motor and said temperature simulator to substantially thesame temperature environment.
 4. A power control system for a vehiclecomprising, a generator having an output winding and a field winding, atraction motor adapted to be connected with a wheel of said vehicle forpropelling said vehicle, means connecting said traction motor with saidoutput winding of said generator, a traction motor temperature simulatorcomprising an electrical heater and a block of heat conductive materiallocated in heat exchange relationship with said heater, means connectingsaid electrical heater in series with said traction motor, saidsimulator being disposed outside of said traction motor, said simulatordeveloping a temperature which is a function of motor current wherebysaid temperature is related to the internal temperature of said tractionmotor, a temperature sensitive resistor located in heat exchangerelationship with said block of heat conductive material for sensing thetemperature of said simulator, control means coupled to said temperaturesensitive resistor and to said field winding of said generator forcontrolling the excitation of said field winding as a function of thetemperature developed by said simulator, and means subjecting saidsimulator and the interior of said traction motor to substantially thesame temperature environment.